That's why this is only 12 chapters. This is the 1950's re-release.

Flash Gordon, the 1936 movie serial had 13 episodes, and a total runtime of nearly 5 hours. So, even with that 13th episode, there would still be about 35-40 minutes of missing footage from the entire serial. And, we may never know exactly what all is missing!
I grew up watching this serial, and knowing that part of it is missing makes me sad! How could someone decide to destroy an important part of cinematic history? What would give someone the right? They do it just because they can? ABSOLUTELY NOT!
Just because you can cut all of the musical numbers from "The Wizard Of Oz", doesn't mean you should! Because, THAT IS NOT YOUR RIGHT TO DO!
Hopefully, the missing episode & footage can be found & restored by someone who knows what they're doing.

Now, this has nothing to do with whoever posted this serial. Fans of this serial are grateful to you. Thank you very much!

Flash Gordon is a historically important science fiction serial, that helped to encourage others in bringing superhero and/or science fiction content to the big screen. It features a vibrant alien planet with great perils for its main protagonist and his friends. The technical aspects are dated, but still work within the context of the narrative. However, the characters are noticeably one-dimensional, which makes the viewing tedious – together with the many repetitions in editing, the score, and plot elements. Aspects like the imaginativeness and the thrilling pacing are very entertaining, but generally this serial does not hold up well, without taking on a nostalgic perspective.
Overall 5/10

Full Review: https://movie-discourse.blogspot.de/2018/02/flash-gordon-usa-1936.html?view=flipcard